U.S. Pat. Nos. 7,160,531 and 7,504,078 both to Jacques et al disclose methods and apparati for the continuous production of aligned carbon nanotubes. Specifically, the aligned carbon nanotubes are produced in arrays comprising a “wheat field” of multi-walled carbon nanotubes (MWCNTs) grown aligned normal to the underlying substrate. In the past the multi-walled carbon nanotubes have been harvested from the substrate for subsequent use in processing with hand-held razors positioned at various acute angles to the substrate. Unfortunately, normally, tight scrolling (inner rolling diameters of less than 2-3 mm) of the array occurs during such a procedure and only small pieces (less than 1 inch squared) are typically recoverable.
The present invention relates to new methods and apparati for harvesting carbon nanotube arrays in a “non-scrolled”, flat, intact condition. The resulting harvested carbon nanotube arrays include vertically aligned MWCNTs forming free-standing films—free from the underlying substrate—with the vertically aligned, “wheat field” morphology intact. Advantageously, the recovery of relatively large, intact carbon nanotube arrays (on the order of between about 100 and about 500 inches squared) provides for a number of advantages including, but not limited to: maintaining the through-thickness axial alignment of the MWCNTs within the array in a free-standing sheet form, un-bound to the original growth substrate; such sheets provide for preferential transport properties, including thermal conductivity, along the nanotube axes, or through the sheet thickness; such free-standing sheets have both upper and lower MWCNT tips exposed; such sheets are compliant and can conform to surface roughness within an interface application; the original MWCNT growth substrates can be re-used in MWCNT synthesis; free-standing sheets can be die-cut into predetermined shapes; such size arrays can be used in applications requiring >100 square inches of continuous array sheets.